Coupled helical wave structure employing a remanently magnetized ferrite



Aprll 4, 1967 I. s. AKMENKALNS ETAL 3,312,915

COUPLED HELICAL WAVE STRUCTURE EMPLOYING A REMANENTLY MAGNETIZED FERRITEFiled Dec. 30, 1965 fifiw fE UTILIZATION 22 FERRITE MEANS 2 /18 9 4i 6 819 29 20 1s 28 PRIMARY V I DETECTQR MICROWAVE 12 14 26 OSCILLATOR SIGNALSOURCE 16 WM 2 -38 T029 T023 UTILIZATION I MEANS DETECTOR FIG 4l/VVE/VTOPS.

IVARS G. AKMENKALNS PHILIP A. LORD @omwy-w United States Patent Office3,312,915 Patented Apr. 4, 1967 3,312,915 COUPLED HELICAL WAVE STRUCTUREEM- PLOYING A REMANENTLY MAGNETIZED FERRITE Ivars G. Akmenkalns,Endicott, and Philip A. Lord, Vestal,

N.Y., assignors to International Business Machines Corporation, Armonk,N.Y., a corporation of New York Filed Dec. 30, 1965, Ser. No. 517,629Claims. (Cl. 333-241) This invention relates in general to coupledhelical wave structures and, more particularly, to a plurality ofhelical wave structures operating on the principle of gyromagneticresonant absorption and a ferrite toroid as the means for controllingthe transmission of a microwave signal from a first helical structure toa second helical structure.

It is generally well known that microwave energy can be absorbed by theferrite material of a microwave structure if the proper conditions forgyromagnetic resonant absorption are created. The term ferrite is usedto refer to that class of magnetic metals which possess extremely highresistivity and permeability. More specifically, the proper conditionsinclude the switching of the ferrite element into its state ofmagnetization so that one electron in the ferrite finds itself in thefield of all the other electrons. That is, the one electron is not freeto move alone in response to an external magnetic field because ofexchange interactions but rather, must respond to the external magneticfield together with its neighboring electrons. Because this type ofelectron has both a magnetic moment and angular momentum, it acts like asmall magnetized top when exposed to an external magnetic field. Whenthe electron is in this external magnetic field, the field attempts torotate the electron so that the two hecome aligned. Like all tops uponwhich such forces act, however, the electron does not line up with thefield but instead precesses or swings about the field direction. With amagnetic field which is rotating in the same sense as the electronprecesses, the electron absorbs energy from the field and tends tobecome disaligned therefrom. This process of the processing electrontending to absorb energy from an external field is .generally known asgyromagnetic resonant absorption. When the external magnetic field isrotating in a sense opposite to that in which the coupled electrons areprocessing or the magnetic field is oscillating at a substantiallydifferent rate of rotation, the magnetic field passes through theferrite substantially undiminished in intensity.

It is an object of the instant invention to provide a coupled helicalwave structure employing a ferrite element as a shielding means forswitchably controlling the coupling of microwave signals from a firsthelical coil to a second helical coil.

It is a still further object of the instant invention to provide acoupled helical wave structure which operates similarly to atransformer.

It is another object of the instant invention to provide a coupledhelical wave structure which is capable of use as a direction coupler.

These and other objects of the instant invention are accomplished by thepresent invention through the use of a cylindrical ferrite elementhaving a central bore. A drive wire threads the bore for switching theelement to either of its stable states of remanent magnetization. Afirst coil is wound on the outer surface of the ferrite element, and asecond coil is placed within the central bore. While the ferrite is inone state of remanent magnetization, microwave energy is coupled fromthe first coil to the second. While the ferrite is in its second stateof remanent magnetization, the coupling is substantially tages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings, wherein FIG. 1 is a partial section taken onthe center line of the1 ferrite element showing the placement of theinner cor FIG. 2 is a standard BH curve associated with magneticmaterial;

FIG. 3 shows an alternate embodiment of the instant invention whereinthe leads to the inner coil pass through the ferrite element; and

FIG. 4 shows the placement of the inner coil away from the ends of theferrite element.

The same numerals are used to identify similar items in each of theseveral views.

Referring to FIG. 1, there can be seen a cylindrically shaped ferriteelement 2 having an outer wall 4 and an inner wall 6. The inner wall 6forms a central bore 8 through which a drive wire 10 and a first helicalcoil 12 are placed. The drive wire 10 transmits bi-polar switchingpulses from a signal source 13 to switch the ferrite element to eitherof its two remanent states of magnetization. The coil 12 is shown havinga right to left pitch and having a constant distance 14 between adjacentturns, however, the direction and pitch is not critical to the operationof the instant invention. The coil 12 has a slightly greater diameterthan the diameter of the bore 8 and the coil is made of resilientmaterial. The coil 12 is drawn slightly, inserted in the bore and thenreleased to regain its original shape. The coil then holds the element 2in a fixed position. An air gap can exist between the coil 12 and theferrite 2 if an alternate method of securing 12 and 2 together isemployed. An end 16 of the coil 12 is connected to a first detector 18,and the remaining end 20 is connected to a utilization means 22. Thedevice has been found to operate better when no portion of the coil 12extends beyond the ends 19 and 19a of the element 2. The utilizationmeans 22 can be a strip line, another detector or any device in general.

A second helical coil 24 is wound around the outer wall 4 of the element2, which coil is shown having a left to right pitch opposite to that ofthe coil 12. A certain direction and pitch of the coil 24 has not beenfound critical to the operation of the instant invention. An end 26 ofthe coil 24 is connected to a source of microwaves 28 by a strip lineand the remaining end 28a is connected to a second primary detector 29.The device has been found to operate better when no portion of the coil24 extends beyond the ends 19 and 19a of the element 2.

In operation, the coupled helical wave structure is selectably switchedto either of its remanent states of magnetization. FIG. 2 shows astandard BH magnetization curve having its two remanent statesidentified as 30 and 32. Assuming the element is driven to its firstremanent state 30 by a positive going: pulse on the drive wire 10, theelectrons in the ferrite are circularly polarized and given a firstsense of rotation. Additionally, the microwave source is activatedsending a microwave signal down the helix 24. The helix causes thesignal to generate a highly circularly polarized magnetic field, alsorotating in the first sense of rotation. Since the microwave frequencyis designed to match the gyromagnetic resonant absorption frequency ofthe ferrite, coupling between the electrons and the field occurs and thefield is partially absorbed by the ferrite to reduce the coupling of themicrowave signal to the helix 12. A first level of microwave energy issensed in the utilization means 22. The primary detector 29 senses areduced level of microwave energy transmitted from the oscillator 28.This reduction is 1 3 attributed to absorption in the ferrite andcoupling to the coil 12.

When the element is driven to its second stable state of remanentmagnetization, its electrons are caused to rotate in a second sense ofrotation. The helix continues to generate a field rotating in a firstsense of rotation so no coupling occurs. The magnetic field penetratesthe ferrite and is picked up by the inner coil 12 and sensed by theutilization means 22. When the ferrite is in that state increasedtransmission to the utilization means is observed since less absorptionoccurs. The signal level at the utilization means is increasedapproximately 20 db. As between the ends 16 and 20 of the inner coil 12,maximum power is available at the end 16.

FIG. 4 shows the ends 16 and 20 of the inner coil 12 spaced from theends 19 and 19a of the element 2. FIG. 3. shows the ends 16 and 20 ofthe inner coil 12 being connected to the detector 18 and the utilizationmeans 22 respectively by wires 34 and 36 respectively passing throughthe walls 4 and 6 of the element 2 through passages 38 and 40respectively.

The instant invention will satisfactorily operate when the element 2 ispremagnetized prior to its assembly into a completed coupled helicalwave structure. In this embodiment a drive wire need not be supplied ifthe state of the element 2 is to remain unchanged.

In summary, the present invention is a four-terminal device having anadditional drive line 10 available to switch the ferrite 2 to either ofits stable magnetic states. A first helix 24 is wound around the outsideof a circular ferrite core 2 and a second helix 12 is placed within acentral bore 8 of the ferrite. A microwave oscillator 28 is applied toone end of the outer helix 24 anda primary detector 29 is attached tothe second end of the helix 24. Different levels of microwave energy aresensed at the primary detector 29 depending upon the switched state ofthe ferrite 2. A detector 18, attached to the near end 16 of the innerhelix 12, receives microwave energy which is substantially independentof the switching action of the ferrite 2. The utilization means 22 isconnected to the opposite end 20 of the inner coil 12 which receivesmicrowave energy dependent upon the switched state of the ferrite 2.

While the invention has been particularly shown and described withreference to preferred embodiments thereof, it will be understood bythose skilled in the art that the foregoing and other changes in formand details may be made therein without departing from the spirit andscope of the invention.

What is claimed is:

1. A coupled helical wave structure comprising,

a ferrite element having a bore positioned therethrough,

said element having an integral gyromagnetic resonant absorptionfrequency,

said element being selectively magnetized to a first stable state ofremanent magnetization and to a second stable state remanentmagnetization,

said magnetized ferrite generating a first circularly polarized magneticfield having electrons with a first sense of rotation corresponding to asaid first stable state of remanent magnetization and for generating asecond circularly polarized magnetic field having electrons with asecond sense of rotation corresponding to said second stable state ofremanent magnetization,

a source of microwave signals operating at substantially said resonantabsorption frequency,

' selected state of remanent magnetization.

3. The coupled helical wave structure as recited in claim 1, whereinsaid element is cylindrically shaped and is premagnetized to saidselected state of remanent magnetization.

4. The coupled helical wave structure as recited in claim 1, and furtherincluding a cylindrically shaped inner wall which forms said bore andwherein said third means is positioned in contact with said inner wall.

5. The coupled helical wave structure as recited in claim 1, whereinsaid element is cylindrically shaped,

said bore is centrally located within said element and is formed by aninner wall, and

said third means is in contact with said inner wall.

6. The coupled helical wave structure as recited in claim 5, whereinsaid element is premagnetized to said selected state of remanentmagnetization,

and further including utilization means responsive to said third means.

7. The coupled helical wave structure as recited in claim 1 and furtherincluding drive means threading said bore for selectively magnetizingsaid element to the desired state of remanent magnetization.

8. The coupled helical wave structure as recited in claim 7, whereinsaid second means is positioned wholly in contact with said element.

9. The coupled helical wave structure as recited in claim 1, whereinsaid element is cylindrically shaped,

said bore is centrally located within said element and is formed by aninner wall, said third means is in contact with said inner wall, saidelement is formed with a plurality of passages connecting said centralbore to external said element, and further including utilization meansresponsive to said third means, and fourth means positioned within saidpassages for connecting said utilization means to said third means. It).The coupled helical wave structure as recited in claim 1, wherein saidsecond means is positioned wholly in contact with said element,

said third means comprises a helical coil having a plu' rality of turns,and said turns comprising the ends of said coil being spaced from theends of said element.

References Cited by the Examiner UNITED STATES PATENTS 2,994,842 8/1961Treuhaft 333-11 ELI LIEBERMAN ,Primary Examiner,

P. L. GENSLER, Assistant Examiner.

1. A COUPLED HELICAL WAVE STRUCTURE COMPRISING, A FERRITE ELEMENT HAVINGA BORE POSITIONED THERETHROUGH, SAID ELEMENT HAVING AN INTEGRALGYROMAGNETIC RESONANT ABSORPTION FREQUENCY, SAID ELEMENT BEINGSELECTIVELY MAGNETIZED TO A FIRST STABLE STATE OF REMANENT MAGNETIZATIONAND TO A SECOND STABLE STATE REMANENT MAGNETIZATION, SAID MAGNETIZEDFERRITE GENERATING A FIRST CIRCULARLY POLARIZED MAGNETIC FIELD HAVINGELECTRONS WITH A FIRST SENSE OF ROTATION CORRESPONDING TO A SAID FIRSTSTABLE STATE OF REMANENT MAGNETIZATION AND FOR GENERATING A SECONDCIRCULARLY POLARIZED MAGNETIC FIELD HAVING ELECTRONS WITH A SECOND SENSEOF ROTATION CORRESPONDING TO SAID SECOND STABLE STATE OF REMANENTMAGNETIZATION, A SOURCE OF MICROWAVE SIGNALS OPERATING AT SUBSTANTIALLYSAID RESONANT ABSORPTION FREQUENCY, SECOND MEANS POSITIONED AROUND SAIDELEMENT AND CONNECTED TO SAID SOURCE FOR CIRCULARLY POLARIZING SAIDMICROWAVE SIGNAL IN SAID FIRST SENSE OF ROTATION, THIRD MEANS POSITIONEDWITHIN SAID BORE FOR MAGNETICALLY COUPLING WITH SAID MICROWAVE SIGNAL ONSAID SECOND MEANS, AND SAID FERRITE IN SAID FIRST STATE OF REMANENTMAGNETIZATION SUBSTANTIALLY ABSORBING SAID MICROWAVE SIGNALS IN SAIDFERRITE AND SAID FERRITE IN SAID SECOND STATE OF REMANENT MAGNETIZATIONSUBSTANTIALLY PASSING SAID MICROWAVE SIGNALS UNDIMINISHED TO SAID THIRDMEANS.